---
- branch: MAIN
  date: Tue Mar 13 02:24:26 UTC 2018
  files:
  - new: '1.211'
    old: '1.210'
    path: src/sys/kern/kern_proc.c
    pathrev: src/sys/kern/kern_proc.c@1.211
    type: modified
  id: 20180313T022426Z.7507c5c18ea4ee4c507d7f55501f74d2c1266113
  log: |
    Make sysctl_doeproc() more predictable

    Swap the order of looking into zombie and all process lists, start now
    with the zombie one. This prevents a race observed previously that the
    same process could be detected on both lists during a single polling call.

    While there:
     - Short-circuit break for KERN_PROC_PID, once a pid has been detected.
     - Removal of redundant "if (kbuf)" and "if (marker)" checks.
     - Update of comments regarding potential optimization, explaining why we
       don't want to it as of now. Performance gain from lookup call vs
       iteration over a list is neglible on a regular system.
     - Return ESRCH when no results have been found. This allows more easily
       to implement a retry or abandon algorithm.

    This corrects races observed in the existing ATF ptrace(2) tests, related
    to await_zombie(). This function was expecting to check whether a process
    has been transformed into a zombie, however it was causing occasional
    crashes as it was overflowing the return buffer, returning the same pid
    twice: once from allproc list and the second time from zombieproc one.

    Fix suggested by <christos>
    Short-circuit break suggested by <kre>

    Discussed on tech-kern.

    Sponsored by <The NetBSD Foundation>
  module: src
  subject: 'CVS commit: src/sys/kern'
  unixtime: '1520907866'
  user: kamil